/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package org.apache.coyote.http11.filters;

import org.apache.coyote.OutputBuffer;
import org.apache.coyote.Response;
import org.apache.coyote.http11.OutputFilter;
import org.apache.tomcat.util.buf.ByteChunk;
import org.apache.tomcat.util.buf.HexUtils;

import java.io.IOException;

/**
 * Chunked output filter.
 *
 * @author Remy Maucherat
 */
public class ChunkedOutputFilter implements OutputFilter {


	// -------------------------------------------------------------- Constants
	/**
	 * End chunk.
	 */
	protected static final ByteChunk END_CHUNK = new ByteChunk();


	// ----------------------------------------------------- Static Initializer

	static {
		byte[] END_CHUNK_BYTES = {(byte) '0', (byte) '\r', (byte) '\n',
				(byte) '\r', (byte) '\n'};
		END_CHUNK.setBytes(END_CHUNK_BYTES, 0, END_CHUNK_BYTES.length);
	}


	// ------------------------------------------------------------ Constructor

	/**
	 * Next buffer in the pipeline.
	 */
	protected OutputBuffer buffer;


	// ----------------------------------------------------- Instance Variables
	/**
	 * Buffer used for chunk length conversion.
	 */
	protected byte[] chunkLength = new byte[10];
	/**
	 * Chunk header.
	 */
	protected ByteChunk chunkHeader = new ByteChunk();

	/**
	 * Default constructor.
	 */
	public ChunkedOutputFilter() {
		chunkLength = new byte[10];
		chunkLength[8] = (byte) '\r';
		chunkLength[9] = (byte) '\n';
	}


	// ------------------------------------------------------------- Properties


	// --------------------------------------------------- OutputBuffer Methods

	/**
	 * Write some bytes.
	 *
	 * @return number of bytes written by the filter
	 */
	@Override
	public int doWrite(ByteChunk chunk, Response res)
			throws IOException {

		int result = chunk.getLength();

		if (result <= 0) {
			return 0;
		}

		// Calculate chunk header
		int pos = 7;
		int current = result;
		while (current > 0) {
			int digit = current % 16;
			current = current / 16;
			chunkLength[pos--] = HexUtils.getHex(digit);
		}
		chunkHeader.setBytes(chunkLength, pos + 1, 9 - pos);
		buffer.doWrite(chunkHeader, res);

		buffer.doWrite(chunk, res);

		chunkHeader.setBytes(chunkLength, 8, 2);
		buffer.doWrite(chunkHeader, res);

		return result;

	}

	@Override
	public long getBytesWritten() {
		return buffer.getBytesWritten();
	}


	// --------------------------------------------------- OutputFilter Methods

	/**
	 * Some filters need additional parameters from the response. All the
	 * necessary reading can occur in that method, as this method is called
	 * after the response header processing is complete.
	 */
	@Override
	public void setResponse(Response response) {
		// NOOP: No need for parameters from response in this filter
	}

	/**
	 * Set the next buffer in the filter pipeline.
	 */
	@Override
	public void setBuffer(OutputBuffer buffer) {
		this.buffer = buffer;
	}

	/**
	 * End the current request. It is acceptable to write extra bytes using
	 * buffer.doWrite during the execution of this method.
	 */
	@Override
	public long end()
			throws IOException {

		// Write end chunk
		buffer.doWrite(END_CHUNK, null);

		return 0;

	}

	/**
	 * Make the filter ready to process the next request.
	 */
	@Override
	public void recycle() {
		// NOOP: Nothing to recycle
	}
}
